Les vacances auxquelles je pense: the holidays about which I am thinking You need to know the French phrasal verbs to know that here the preposition is “à”: penser à (to think about)

L’arbre près duquel je suis tombé: the tree near which I fell Près de = near, so the preposition is “de”.

With the preposition “de”, we have two relative pronouns: duquel and dont

Duquel is for things and animals Dont is for people, things and animals

So, when the preposition “de” is for someone, we use “dont” and when we have the choice (because it is about things or animals) we also use “dont”. As you can see, “duquel” is not used a lot. So, “dont” is the translation of “whose”, because “whose” is “of who” or “of which”: Look at my friend whose uncle (uncle of whom) is a journalist: Regardez mon ami dont l’oncle est journaliste. We use “duquel”, when the preposition “de” is part of a bigger expression like “près de: near”, “au bout de: at the end of”, “au sujet de: about”, “au milieu de, in the middle of”…